Understanding the Official Scrabble Word List: NWL, CSW, and OSPD Explained

What Is the Official Scrabble Word List?

If you play Scrabble regularly, you have probably wondered which words are allowed and why some common words you know are rejected while obscure ones are accepted. The answer lies in the official Scrabble word list. This is not a single universal dictionary but a set of word lists maintained by tournament organizations and dictionary publishers. The lists define the playable vocabulary for the game, and they differ depending on where you play and what rules you follow.

The idea behind a Scrabble word list is simple: it gives players a fixed, agreed-upon set of words that are valid in the game. Without such a list, disputes would be endless. The list is not about correctness in everyday English; it is about what is acceptable for the purpose of scoring points. Knowing which list your game uses can help you choose better words, avoid challenges, and improve your play.

The Three Major Lists: NWL, CSW, and OSPD

Three word lists dominate Scrabble play. They are NWL (North American Word List), CSW (Collins Scrabble Words, also known as the international list), and OSPD (Official Scrabble Players Dictionary). Each serves a different audience, and each has its own set of accepted words. Understanding the differences can save you from frustration during a game.

NWL: The North American Standard

NWL is the word list used in official Scrabble tournaments and clubs in North America. It is maintained by the North American Scrabble Players Association (NASPA). NWL is updated periodically to reflect changes in the language, but the updates are conservative. New words are added only after they have appeared in common use over time. NWL tends to be smaller than CSW, with fewer obscure or foreign words. For most casual players in the United States and Canada, NWL is the default list. If you buy a Scrabble board in North America, the included word list is usually based on NWL or its predecessors. When you use a Scrabble word checker tool, you often have the option to check words against a dictionary that uses NWL data.

CSW: The International Word List

CSW, published by Collins, is the word list used in international Scrabble tournaments and in many other parts of the world. It is larger than NWL and includes many words from British English, Australian English, and other regional varieties. CSW also accepts more two-letter words, three-letter words, and obscure terms that are not valid in NWL. For example, words like "qi" (a variant of chi) and "za" (slang for pizza) are in CSW but not always in NWL. If you play Scrabble online against opponents from different countries, you are likely using CSW. The list is also used in the World Scrabble Championship. Knowing that CSW is more permissive can help you decide when to challenge a word or when to try a risky play.

OSPD: The Reference Dictionary

The Official Scrabble Players Dictionary is a published book that contains the word list for North American play. It is based on NWL but includes definitions, part-of-speech labels, and example sentences. Many casual players own a copy of OSPD to settle disputes. The dictionary is updated in editions, with the latest edition (OSPD5) containing about 100,000 words. OSPD is not a separate word list per se; it is a printed version of the North American list. However, because it includes definitions, it can be more useful for learning new words than a bare list. When you check words against a dictionary in a physical book, you are using OSPD. For online tools, the word list behind the scenes is often NWL or CSW, not the dictionary itself.

How Word Lists Are Created and Updated

Word lists are not arbitrary. They are compiled by lexicographers and Scrabble experts who review sources such as major dictionaries, newspapers, magazines, and online usage. The process is similar to how a general dictionary is created, but the criteria are different. For Scrabble, a word must appear in at least two independent sources to be considered. The word must also be in common use, though "common" is interpreted broadly. The lists are updated every few years to add new words that have entered the language, such as "selfie" or "emoji". Outdated words may be removed, though this is rare. The updates are announced in advance, and players have time to learn the new words.

One important detail: the word list does not include proper nouns, abbreviations, or words that always start with a capital letter. Exceptions exist for some words that have moved into common usage, like "jazz" or "internet". But generally, if a word is a name, it is not allowed. This rule prevents players from using obscure place names or brand names.

Regional Differences and Tournament Rules

The choice between NWL and CSW matters most in competitive play. In North American tournaments, NWL is the standard. In international tournaments, CSW is used. If you travel to play in Europe, you need to be comfortable with CSW. The difference is not huge in terms of number of words, but it can affect high-scoring plays. For example, the word "ae" (a variant of "a") is valid in CSW but not in NWL. Similarly, "oe" (a whirlwind) is in CSW only. These two-letter words can be crucial for parallel plays.

In casual home games, the rule is whatever the players agree on. Many households use the list that came with the board, which is usually the North American list. If a player challenges a word, you can look it up in the dictionary or use an online tool. The important thing is to have a shared understanding of which list you are using before the game starts. Disagreements over words are common, and having a clear reference avoids arguments.

What This Means for Your Game

Knowing which word list applies to your game can help you make better decisions. If you are playing in a tournament, study the specific list used there. For casual play, you can choose the list that feels right for your group. Many online Scrabble tools let you switch between NWL and CSW. When you check words against a dictionary, you can see whether a word is valid in both lists or only one. This can help you avoid playing a word that will be challenged.

Another practical tip: learn the two-letter words in your list. They are the foundation of many plays, especially when you are stuck with tiles like Q, Z, or J. The two-letter word list differs between NWL and CSW, so check which one you are using. For example, "da" is valid in CSW but not in NWL. "Gi" (a type of martial arts uniform) is in CSW only. Knowing these differences can give you an edge.

Using a Scrabble Word Checker

A good Scrabble word checker can help you verify words and find playable options. These tools use the official word lists to validate words. When you type a word, the tool checks it against the chosen list and tells you whether it is valid. It also provides the point value and often the definition. This is useful for learning new words and for settling disputes. Many checkers also let you enter your rack letters and find all possible words. This feature is especially helpful when you are stuck. The key is to ensure the tool uses the correct list for your game. If you are playing with CSW, make sure the checker is set to that list.

In summary, the official Scrabble word list is not a single monolithic document but a family of lists tailored to different regions and levels of play. NWL and CSW are the two main competitive lists, while OSPD is the published dictionary for North American players. Knowing which list you are using can improve your strategy and reduce arguments. Whether you are a casual player or a tournament competitor, understanding the word list is part of mastering the game. Next time you play, take a moment to agree on which list you will use. It will make the game smoother and more enjoyable for everyone.